Positive Train Control Myths and Facts

Now that installation of PTC is mandated by Federal law, I continue to be surprised by the lack of knowledge (even among railfans) about what it is and what it does. in part, I think, this is because FRA chose to write a functional specification rather than a prescriptive regulation -- there are several different ways of meeting the statutory requirements. I'll attempt to briefly summarize a complex topic (I've been working on PTC-related issues on and off since 1988).

1) PTC is required by statute on all tracks carrying more than 5 MGT of freight traffic, on all tracks carrying passenger trains -- with some exceptions -- and on all tracks over which any volume of TIH is moved. The statute only covers Class I railroads; Class II and Class III carriers are exempted, and passenger trains operating on those carriers may also be exempted, on an individual basis, by the Secretary of Transportation.

2) There are two distinct "flavors" of PTC. One is the ETMS-type system well described in the video link posted earlier on this thread. This is a "vehicle-centric" system; vehicle borne computers determine train position and speed and enforce authorities transmitted directly from the central office. The only equipment on the wayside is radio repeaters and "wayside interface units" that monitor switch position and grade crossing activation. WIUs are very cheap and simple devices. The other flavor of PTC is what I call "wayside-centric". In this arrangement, most communications are between wayside devices (either track-mounted transponders, as in Amtrak's ACSES, or wayside "beacons" in ITCS) and trains. The wayside devices transmit authorities and grade crossing and switch data, as well as maximum speeds. There need not, in these systems, be any communication between trains and the central office. In this respect, ACSES and ITCS are like conventional cab signal systems.

3) The information generated by a vehicle-centric PTC system can be used for a host of other functions, such as dispatch planning, schedule adherance, locomotive health monitoring, status of en-route pickups and set-outs, etc. Some people (and I am one) believe that the availability of real-time train location data will enable railroads to realize substantial operating efficiencies. The railroads deny this. But for example, how much more efficient will track maintenance become when a foreman knows, to the minute, when the next train will show up?

4) To say ETMS-type systems are "GPS based" does not mean they rely exclusively on GPS, and that the whole railroad will come to a halt if the GPS signal is lost. Position is also determined by odometers, accelerometers, and triangulation from radio towers (just as cell phones do). And of course, once an authority is issued, the train can proceed to its limit even if GPS is lost (or even if radio contact is lost). No new authorities can be issued, of course, until communications are restored. Also remember that all Class I railroads have encoded their tracks into GIS databases, so if you monitor switches, you know which way the train went at the last switch, so there is no problem in discriminating between two tracks on a double-track line -- unless the train is not on the track, in which case you have other problems.

5) Since much of the cost in vehicle-centric systems is either on the locos or in the central office, the current carping over the percentage of the system that must be equipped is a canard. Since all locomotives will have to have the equipment, and all tracks on Class I railroads also have voice radio coverage, the most rational thing to do is equip the entire network. Digital radios can be sited at the same locations as existing radio base stations. Switch position indicators are already required (they can be visible targets) even on unsignaled track, and WIUs are cheap.

6) Similar objections concerning the difficulty of calculating a braking algorithm are also red herrings. In 1989, on the Iron Range of Minnesota, I watched a dispatcher remotely intervene and stop a 22,000 ton ore train. It stopped right where it needed to, just short of a red home signal. If BN could do that in 1988 with an 8086 processor and 4800 baud digital data link, I have trouble believing it can't be done today with processors and data links much faster than those. AAR has conjured up some worst case scenario of a train with non-functional dynamic brakes (which loco health monitoring would detect in a PTC system) and 15% inoperative train brakes (for which FRA would fine a railroad for letting a train like that leave a terminal). There are already "adaptive" braking algorithms that "learn" how a particular train handles, and I have no doubt that they'll do a better job than many human engineers. I speak from the perspective of having run a lot of different train simulation packages over the last 20 years.

So despite all the moaning and grumbling, I'm confident, first, that PTC will work (I can't see any insuperable technical difficulties -- after all, BN had a working prototype more than 20 years ago), and second, that it will turn out to produce substantial operating benefits for railroads. So let's quit complaining and go do it. The law gives the railroads five years.

Similar objections concerning the difficulty of calculating a braking algorithm are also red herrings. In 1989, on the Iron Range of Minnesota, I watched a dispatcher remotely intervene and stop a 22,000 ton ore train. It stopped right where it needed to, just short of a red home signal. If BN could do that in 1988 with an 8086 processor and 4800 baud digital data link, I have trouble believing it can't be done today with processors and data links much faster than those. AAR has conjured up some worst case scenario of a train with non-functional dynamic brakes (which loco health monitoring would detect in a PTC system) and 15% inoperative train brakes (for which FRA would fine a railroad for letting a train like that leave a terminal). There are already "adaptive" braking algorithms that "learn" how a particular train handles, and I have no doubt that they'll do a better job than many human engineers. I speak from the perspective of having run a lot of different train simulation packages over the last 20 years.

I am not familiar with operations on this particular railroad, but I have never heard of a dispatcher having the authority, or ability to interfere with the physical movement of a train. Locomotive Engineers are not "babysat".
Non-functional dynamic brakes? Worse case scenario? Right....
So you believe you have even the smallest idea of train handling because you "run a lot of different train simulation packages over the last 20 years."? Please, quit while you are ahead, you do not have a clue as to what you are talking about. No computer, regardless of how "smart" it is, will be able to replicate the train handling skills, physical characteristic, and rules knowledge of a good Engineer. Instead of running your train hot into that 40 curve, entering exactly at 40 with the throttle open because you are charging upgrade, the new braking envelope will have you doing 40, 3 trainlengths before the restriction, struggling at 30 because you lost all your momentum. I will be surprised if the system will know much more about train handling other than PCS Open, Emergency, Full Service and Release. With larger freight trains, sounds like a great way to make a mess...

I went to the TRB conference in DC this year and people that I talked with basically said there is no way it was going to happen. The industry would take a shot at it, but nobody was very optimistic. As it stand now they would have to install more signaling in a shorter amount of time that has ever been done before. The only reason that PTC was mandated was because the signaling vendors were able to lobby for it. For years the NTSB had basic "cab signals" as their #1 most wanted safety improvement. Then sometime around 2007 it changed to "PTC" because signal industry lobbyists got involved. As soon as congress fails to appropriate the $15 billion cost we'll see what the railroad industry lobby has to say about things.

3) The information generated by a vehicle-centric PTC system can be used for a host of other functions, such as dispatch planning, schedule adherance, locomotive health monitoring, status of en-route pickups and set-outs, etc. Some people (and I am one) believe that the availability of real-time train location data will enable railroads to realize substantial operating efficiencies. The railroads deny this. But for example, how much more efficient will track maintenance become when a foreman knows, to the minute, when the next train will show up?

Like it or not, EVERY new safety relate

d system has slowed down operations. If you want the best headways you run on sight and live with the occasional accident. For example the new L train CBTC has slowed the peak throughput from 22tph to 20tph. The target benefit was only 24tph so even if CTBC had worked as advertised one would only have gotten an extra 2 tph extra compared with the traditional system. BTW All of the ancillary benefits you outlines can be done with something called a smart phone for a lot less cost.

4) To say ETMS-type systems are "GPS based" does not mean they rely exclusively on GPS, and that the whole railroad will come to a halt if the GPS signal is lost. Position is also determined by odometers, accelerometers, and triangulation from radio towers (just as cell phones do). And of course, once an authority is issued, the train can proceed to its limit even if GPS is lost (or even if radio contact is lost). No new authorities can be issued, of course, until communications are restored. Also remember that all Class I railroads have encoded their tracks into GIS databases, so if you monitor switches, you know which way the train went at the last switch, so there is no problem in discriminating between two tracks on a double-track line -- unless the train is not on the track, in which case you have other problems.

That's fine if you are on some secondary track with blocks 10 miles long, but what if you are on a main line with short signal blocks? If you lose contact even for a minute you'll run into a penalty brake application. The wireless CBTC type PTC is simply not going to fly on busy main lines. Even if the more reliable coded track circuit type PTC is used I'm sure there will be problems. Notice how Amtrak has not installed ACSES on any of its more complex pieces of mainline. Right now its in service (approximately) between REGAN and PRINCE, HAM and UNION and Mill River and Providence. Those are all pretty much straight rail with little complex trackwork.

So yeah, if you want to install it on low density DCS territory go nuts, but don't assume what works for Rural Route 9 will work for I-95.

5) Since much of the cost in vehicle-centric systems is either on the locos or in the central office, the current carping over the percentage of the system that must be equipped is a canard. Since all locomotives will have to have the equipment, and all tracks on Class I railroads also have voice radio coverage, the most rational thing to do is equip the entire network. Digital radios can be sited at the same locations as existing radio base stations. Switch position indicators are already required (they can be visible targets) even on unsignaled track, and WIUs are cheap.

Data radios operate in a higher frequency band that doesn't get as much coverage and the existing voice network isn't 100% reliable. Think about it, does your new digital TV work as well as your analogue one did?

6) Similar objections concerning the difficulty of calculating a braking algorithm are also red herrings. In 1989, on the Iron Range of Minnesota, I watched a dispatcher remotely intervene and stop a 22,000 ton ore train. It stopped right where it needed to, just short of a red home signal. If BN could do that in 1988 with an 8086 processor and 4800 baud digital data link, I have trouble believing it can't be done today with processors and data links much faster than those. AAR has conjured up some worst case scenario of a train with non-functional dynamic brakes (which loco health monitoring would detect in a PTC system) and 15% inoperative train brakes (for which FRA would fine a railroad for letting a train like that leave a terminal). There are already "adaptive" braking algorithms that "learn" how a particular train handles, and I have no doubt that they'll do a better job than many human engineers. I speak from the perspective of having run a lot of different train simulation packages over the last 20 years.

How does an algorithm learn what the weather conditions are and how they affect train handling? If you are in a train and it starts to rain do you hit a rain button or do the speed algorithms just assume that the tracks are always covered in ice? What happens when a train following the dry braking curve slides past a signal on wet track and the algorithms are required to assume the tracks are always covered in ice and travel times on Amtrak trains increase by 20%?

BTW, do you realize that 22,000ton ore train is HOMOGENEOUS!! Every car ore car is the same and carries the same load. That's a piece of cake to calculate stopping curves for. Also, what is the grade profile of the line? Florida East Coast is the only major freight railroad currently using cab signal w/ speed control and surprise surprise Florida is COMPLETELY FLAT. Finally how do you teach a PTC system when its better to let a train exceed the stopping parameters because applying the air brake will lead to a runaway situation?

Come 2016 I think there's better than even odds that this mandate will have been relaxed by congress. There is no reason to have PTC in unpopulated areas of the country. There is no reason to have PTC where passenger or TIH cargo is minimal. Hell, given that cab signals would have prevented the Chatsworth accident there is no reason to install PTC period. If Congress doesn't change the law the FRA has wiggle room to write waivers. I mean if its 2016 and the Class 1's don't have PTC working what is anyone going to do? Stop the trains? Once the power goes out someone will change their tune in a hurry.

PTC is the result of lobbyists, not any sort of rational decision making process. Just like the 800,000 pound buff strength requirements were a result of Bombardier wanting to monopolize the North American passenger car market. Whatever happens nobody should fool themselves that PTC does anything other than add "safety" and more safety always slows things down.

well , in tests here , in very hilly country , only a few engineers could get anywhere near the computer simulator as far as fuel economy vs overall time was concerned . they can now monitor this route , and the engineer that has the best fuel economy results each week , gets free petrol ( gas) vouchers .

The PTC/SES system that was being tested on NJT's Pascack Valley Line was a HORRIBLE failure, and after 10 years, and nearly 100 MILLION dollars (number I was told, I have not verified it) it was relatively recently SCRAPPED - done, gone, ripped out. It didn't work, the transponders wouldn't get read, temporary restrictions were a nightmare, braking profiles were set for an absolute worse case scenario, meaning a huge and heavy freight train, which didn't help the 4-5 car lightweight passenger train equipped with disc brakes that can stop from track speed in a trianlength or two. it was constantly failing, and engineers were often having to cut out the SES system just to get the trains over the road. It was replaced with a cab signal/no automatic wayside signal system, aka Norac rule 562.

I am hoping that a simple kind of upgrade to the cab signal systems would be implemented for the PTS. Something like if the cab signals loose their code, and display a restricting in the cab for more than say 6 to 8 seconds, the train MUST be stopped, and a code punched in. This would work for stopping at stop signals, but would allow for cab signal flips and various other quirks that occur out on the railroad. A standard code would be punched in for stopping at stop and proceeds, and the engineer would also have to put a code in if running at restricting, or maybe the system could recognize the differnece inbetween running under a Restricting or have another standard code for restricting, while only stop signals would have an individual code, issued by the dispatcher. Also, clearly marked signs would be nice - say 100 feet in front of signal - "stop in here, and you will need code" but stopping outside of the zone, wouldn't require an imput of a code, especially when the signal would soon come up when following a train, waiting to cross over, etc. An issue in heavy traveled and congested areas where trains often wait for others and follow and cross over.

Simulations might be accurate, but they will never replicate the "feel of the seat of your pants" that the engineer has of his train. the feel of the train it pushing or pulling you, slack run in (VERY important, with passenger and freight, can a simulator replicate that?), stretch or bunching of tran, etc etc etc.

For example, I had a 4 car push pull passenger train today, with a GP40 pushing - but the cars had a lot of slack inbetween them, and even though the speedo didn't change when the slack would run in, you could feel it, and it could knock you over. So I had to adjust how I ran and braked to minimize slack action to prevent passenger injuries - I had to keep the train bunched up by keeping power on til the brakes really set, and then getting off the power and letting dynamics kick on gently, not all at once. Once we got into the yard though, it was like a washing machine.

But what im trying to say is that there is SO much more than running a train than just complying with signals on a simulator. Many engineers don't even use gauges and meters for power or brake. Its all by feel. I often don't use my air guages until im stopped to make sure I have enough brake cylinder on to comply with company rules. I can feel what the train is doing and how the brakes and wheels are warming up and starting to grab more and more and stop better and better. Guages don't help me with that..........

FYI to all. Amtrak is looking o equip the entire NEC with ACSES. It's just a matter of time and money to do it all.

FYI to all. Amtrak is looking o equip the entire NEC with ACSES. It's just a matter of time and money to do it all.

Yes they are looking to, but ACSES is the most reliable, most backward compatible form of PTC currently available and Amtrak is still hesitant to put it in everywhere. Just shows you what the freight railroads have to look forward to.

Remember, every dollar spent on this crap is a dollar that can't be used in moving freight and passengers off of our nation's highways where nearly 40,000 people die each and every year.

Hi Jersey Mike, just a quick correction, the ACSES runs from County to Ham , not Union to Ham...

Jtgshu , i can see the point you are making , and i'm not advocating replacing the engineer .
but , can an engineer feel whats going on in a 150 car frieght train , well , more than the first few cars . i know here , trains have run up to 10 miles before the engineer has relaised cars at the back of the train have derailed ???

Jersey Mike:

PTC (not "cab signals") has been on the NTSB's "most wanted" list since 1992.

And I was at the same TRB session you were. The railroads are just going to have to make it work by 2015. There is zero chance Congress will change the law.

As often the case, i sincerely respect the body of knowledge we can put forth at the forum, especially both sides of this issue regarding PTC as mandated under RSIA08.

Again I note the 'advocates" within the FRA use as their poster children Chatsworth and Graniteville. Even though I never had any exposure to C&S matters during my industry career, I am quite certain that PTC would have avoided Chatsworth and could well have avoided Graniteville. However, again I ask to what extent, if any, could have PTC avoided either Weyauwega or Rockford?

Finally, allow me to ask at present what percentage of Miles of Road Operated (that's a technical term found in the STB's Form R-1 as well as other documents) over which multi frequency passenger trains are operated presently have some form of train control system beyond lineside signals? My guess is at least 50%.

Jersey_Mike wrote: Just like the 800,000 pound buff strength requirements were a result of Bombardier wanting to monopolize the North American passenger car market. Whatever happens nobody should fool themselves that PTC does anything other than add "safety" and more safety always slows things down.

Now there is an untrue statement , The 800 000 Lbs buff strenght have been in effect for(at least) last 40 years, long before Bombardier ever made its first Skidoo.
even 1956 RDC's were made with those requirements, only thing changeed in last few years is requirement of corner coliision post.

David Benton wrote:Jtgshu , i can see the point you are making , and i'm not advocating replacing the engineer .
but , can an engineer feel whats going on in a 150 car frieght train , well , more than the first few cars . i know here , trains have run up to 10 miles before the engineer has relaised cars at the back of the train have derailed ???

Fortunately, or unfortunately, depending on how you (and I) look at it, I have never run a 150 car freight, however, for an engineer on a commuter railroad, I have run my fair share of work trains, with loaded hoppers with stone, loaded gons with ties, and various equipment moves that use straight air, and my longest has been about 35 cars, but from my "trolley railroad" experience, how those first cars react is a pretty good indication of what the rest of the train is going to be doing. The engineer might not be able to feel the slack running in inbetween the 130th and 131st car, as there are literally many feet of slack on a train that long, but the engineer has to know by experience what is going on by there.

And of course, the old RR saying of "dust is bad" applys. Its important to look back and inspect the back of your train when going around curves. One of the drawbacks of not having cabooses, but the railroad has determined that the cost savings of that is greater than the potential of a long freight train dragging a few derailed cars on the hind end.

You can't feel it, but you can visualize it. and operate accordingly. Don't do that, and your conductor is taking a long walk back, and hes not gonna be happy when he gets back.

back to PTC, pardon my ignorance, but how would/can it work on roads WITHOUT cab signals? I understand that PTC has been on a wishlist for a long time by the feds, but would installng cab signals ATC/ATS be a more realistic goal? Sure, cab signals aren't going to prevent every collision, and collisions can still happen in cab signal territory, but they tend to in much lesser numbers. (of course, you can't forget about Chase MD)

This seems to be an incredible burden placed on the railroads, and seems like it was a knee jerk reaction to an incident by politicans who really don't understand the scope of what they want the railroads to do...

Jtgshu wrote:This seems to be an incredible burden placed on the railroads, and seems like it was a knee jerk reaction to an incident by politicans who really don't understand the scope of what they want the railroads to do...

I'm sure it is an incredible financial burden placed on the railroads. Never-the-less, Congress has been patient through recent years, listening at the railroads promising to do better after each preventable passenger train accident. It wasn't a single incident, but a string of multiple incidents. The railroads utterly and completely failed to stop preventable passenger train accidents.

Your suggestion of installing cab signals is a good one that the train industry could have implemented much sooner on their own, but they didn't. The railroads hewed and hawed over passenger safety, challenging Congress to act. Of course government does what it does best, enacted legislation selecting the most expensive and what is believed to be the most reliable solution. Railroads in Asia and Europe have been very successful avoiding accidents using positive train controls. You can't blame Congress mandating postive train controls because foreign nations railroads have proven it works.....

My point is, it's too late crying over spilt milk, the railroads can only blame themselves for not coming up with a solution themselves. I think all transportation companies forget at times that the life and health of just one passenger is worth all the profits they will ever receive from all their other cargos.

electricron wrote:

Jtgshu wrote:This seems to be an incredible burden placed on the railroads, and seems like it was a knee jerk reaction to an incident by politicans who really don't understand the scope of what they want the railroads to do...

I'm sure it is an incredible financial burden placed on the railroads. Never-the-less, Congress has been patient through recent years, listening at the railroads promising to do better after each preventable passenger train accident. It's just that the railroads utterly and completely failed to stop preventable passenger train accidents.

Your suggestion of installing cab signals is a good one that the train industry could have implemented much sooner on their own, but they didn't. The railroads hewed and hawed over passenger safety, challenging Congress to act. Of course government does what it does best, enacted legislation selecting the most expensive and what is believed to be the most reliable solution.

My point is, it's too late crying over spilt milk, the railroads can only blame themselves for not coming up with a solution themselves. I think all transportation companies forget at times that the life and health of just one passenger is worth all the profits they will ever receive from all the other cargos.

Its ironic in a sense to me. the Gov't is pushing green this green that and the railroads are a key component to that, in both passenger and freight operations. However, placing a rediculously heavy burden on the railroads is only going to hurt us as a whole, because do you honestly think the privately owned Railroads are just going to absorb that cost and not pass it along? HAHAHAHAHAH

Shipping rates will go up, therefore, the costs of products will go up, and some shippers might leave railroads all together, and go back to trucking. Placing more pollution in the air, and causing more wear and tear to our already fragile highways and bridges, and more car vs. truck accidents, and they tend to more deadly to those passengers in the cars than the trucks. Roads tend to be MUCH deadlier than railroads, so forcing more freight on to roads is going to end up killing more people than saving lives on railroads with a PTC system. And what happens when there is an accident after PTC is installed? Its GOING to happen, and people WILL die. This isn't going to prevent all future accidents and deaths, no matter how much politicans want it to.

I also find it ironic that the gov't wants this nationwide, when the NEC doesn't even have it yet, and the NEC has areas that are 100 percent passenger trains, with NO freight interference. I mean, even parts of the NEC still use Form Ds and are "dark territory!!!" And most times, those Form Ds and dark territory are used for freight/work trains!!!! And thats even in areas were ACSES is installed!!! (Inbetween Midway and County interlockings in NJ is often used by freight and Amtrak work trains is what comes to mind, and I do believe that 135mph territory for Acela....)